A place to exercise ideas before writing about them with greater discipline.

Tuesday, May 19, 2009

The Need for Competing Hypotheses

This morning BBC NEWS Web site released a story with interesting data and an even more interesting interpretation:

Newly-released US census figures show a strong slowdown in the birth-rate that began before the economic crisis hit.

The number of babies born grew by only 0.9% in the year to July 2008, compared with a rise of 2.7% the year before.

The figures have given rise to speculation that families anticipated hard times by having fewer children.

"If prospects look worse for families, they're going to be very likely to have fewer kids," said Mark Mather of the Population Research Bureau.

The surprising part of the figures is that they reflect family planning decisions made from early 2007, when there were only a few signs of an economic slowdown in the US.

The first real sign of the financial meltdown was in August 2007 when credit markets froze up, but unemployment was still low and consumer confidence high.

'Holding back'

Stephanie Ventura, a demographer at the National Center for Health Statistics, which compiled the figures, told the Associated Press news agency it was too early to be sure why there were fewer pregnancies.

But "it is a very good question" to ask about the effect of the economic slowdown, she said. "They might have wanted to hold back" until economic conditions were more settled.

I have no argument with Ventura: The question is definitely a good one. A better question, however, is why, in the face of such interesting data, there should be such a rush to jump on a single hypothesized interpretation, particularly when that interpretation embodies the classical logical fallacy of affirming the consequent. For example, could the decline be due to families more interested in short-term consumerist indulgences than in making the long-range financial commitments associated with raising a child? Under that hypothesis the addictive grip of consumerism could be considered as a predisposing, if not functional, cause of both the current economic crisis and the decrease in pregnancies. What troubles me about the hypothesis covered in this BBC report is that its causality is more mystical than either predisposing or functional; and such a hypothesis, in turn, could engender a cultural bias that prefers the mystical to the logical. At a time when it has become fashionable to worry about whether Google is making us stupid, do we now have to start worrying about the BBC as well?